Breathing apparatus

Abstract

A forced air breathing apparatus which includes a face piece (20a) for covering at least the nose or mouth of a wearer, a pump unit (10) arranged to supply air to a space within the face piece (20a), a filter (13) to filter air entering the face piece (20a) and valve means to control the flow of air from the pump unit (20) to the face piece (20a) during inhalation and from the face piece (20a) during exhalation. The pump unit (20) includes a fan (12) driven by an electric motor (11). The valve means includes an air inlet valve (19) and an air outlet valve (22), the air outlet valve (22) being maintained in a closed position during inhalation through the air inlet valve (19) by air pressure from the pump unit (20) and being opened by exhaled air. The exhaled air also acts to close the air inlet valve (19) and prevents the entry of exhaled air to the pump unit (20). The fan (12) is a centrifugal fan driven at a substantially constant speed. A valve (14) is provided on the air inlet side of the pump unit (10) and is arranged to close when a defined air pressure is present within the pump unit (10) downstream of the fan (12).

We claim: 
     
       1. A forced air breathing apparatus comprising a face piece or mask covering at least the nose or mouth of a wearer, a pump unit arranged to supply air to a space within the face piece or mask, an electric motor within the pump unit arranged to drive a fan forming part of the pump unit, a filter to filter air entering the face piece or mask and a valve means controlling the flow of air from the pump unit to the face piece or mask during inhalation and from the face piece or mask during exhalation, the valve means including an air inlet valve and an air outlet valve, the air outlet valve being maintained in a closed position during inhalation through the air inlet valve by air pressure from the pump unit and being opened by exhaled air which also acts on the inlet valve to prevent the entry of exhaled air to the pump unit. 
     
     
       2. A forced air breathing apparatus as claimed in claim 1 in which the apparatus includes means for maintaining and controlling the speed of the motor so that the fan rotates at a substantially constant speed during its operation. 
     
     
       3. A forced air breathing apparatus as claimed in claim 2 in which the fan is a centrifugal fan. 
     
     
       4. A forced air breathing apparatus as claimed in claim 1 in which the apparatus includes a valve controlling the flow of air through the pump unit, the valve being arranged to close when the pressure present within the breathing apparatus downstream of the fan rises to a predetermined level. 
     
     
       5. A forced air breathing apparatus as claimed in claim 1 in which the apparatus is provided with actuable control means adapted to cause the apparatus to undergo a calibration phase such that the speed of rotation of the fan is set at a predetermined optimum base value relative to the operating conditions then prevailing in the apparatus. 
     
     
       6. A forced air breathing apparatus as claimed in claim 5 in which the actuable control means includes electronic data processing means which monitors and controls the speed of the motor so as to ensure adequate air flow at the face piece or mask of the apparatus. 
     
     
       7. A forced air breathing apparatus as claimed in claim 6 in which the electronic data processing means includes means to enable a user to enter into the electronic data processing means parameters relevant to the filter type and/or the flow resistance of the apparatus. 
     
     
       8. A forced air breathing apparatus as claimed in claim 6 in which the electronic data processing means includes means adapted to automatically read from the filter in the apparatus parameters relating to that filter. 
     
     
       9. A forced air breathing apparatus as claimed in claim 6 in which the electronic data processing means includes a pressure sensor and/or a flow measurement apparatus adapted to measure the pressure of air in the apparatus and the flow of air through the apparatus, preferably at a location proximate, and downstream of, the filter. 
     
     
       10. A forced air breathing apparatus as claimed in claim 9 in which the pressure sensor comprises a flexible membrane arranged to flex with changes in pressure, an ultrasound transmitter arranged to direct ultrasound at the membrane, an ultrasound receiver to detect ultrasound reflected from the membrane, and an analysing means, the analysing means being capable of determining a parameter based on the transit time of the ultrasound between the transmitter, the membrane and the receiver and calibrated so as to provide an indication of air pressure to the electronic data processing means. 
     
     
       11. A forced air breathing apparatus as claimed in claim 10 in which a temperature probe is included in the electronic data processing means and located proximate the pressure sensor, the temperature probe communicating to the analysing means a signal indicative of measured temperature to allow the analysing means to apply a compensating algorithm to the transit time in accordance with the measured temperature. 
     
     
       12. A forced air breathing apparatus as claimed in claim 1 in which the apparatus includes performance monitoring means for some or all of the parts of the apparatus, which means provides at least one signal that informs the wearer of the condition of some or all of the parts, the signal being generated externally at the face piece or mask and is fed to the face piece or mask for detection by a wearer. 
     
     
       13. A forced air breathing apparatus as claimed in claim 12 in which the performance monitoring means includes a pressure transducer which detects the air pressure within the apparatus, preferably proximate the fan. 
     
     
       14. A forced air breathing apparatus as claimed in claim 12 in which the performance monitoring means monitors the condition of at least one member of the group comprising the power source, the filter, or the pump unit. 
     
     
       15. A forced air breathing apparatus as claimed in claim 12 in which the warning signal is a light source, preferably a light emitting diode, which is transmitted to the face piece or mask by optical fibre. 
     
     
       16. A forced air breathing apparatus as claimed in claim 12 in which the warning signal is an audible tone transmitted to the face piece or mask by an air hose serving as a sound pipe. 
     
     
       17. A forced air breathing apparatus as claimed in claim 1 in which the apparatus is adapted to deliver at least 150 liters of air per minute, preferably at least 300 liters of air per minute, more preferably at least 500 liters of air per minute, to a wearer. 
     
     
       18. A forced air breathing apparatus as claimed in claim 1 in which the apparatus is adapted to supply air to the air inlet valve admitting air to the face piece or mask at a pressure between zero and 10 mBar, more preferably no more than 6 mBar, above ambient reference pressure. 
     
     
       19. A forced air breathing apparatus as claimed in claim 1 in which the filter is positioned between the pump unit and the face piece or mask. 
     
     
       20. A forced air breathing apparatus as claimed in claim 19 in which the apparatus includes a valve controlling the flow of air through the pump unit, the valve being arranged to close when the pressure present within the breathing apparatus between the filter and the face piece or mask rises to a predetermined level. 
     
     
       21. A forced air breathing apparatus as claimed in claim 1 in which the air outlet valve is in flow communication with the pump unit during inhalation and exhalation. 
     
     
       22. A forced air breathing apparatus as claimed in claim 1 in which the pump unit pumps air acting directly on the air outlet valve to maintain the air outlet valve in the closed position during inhalation. 
     
     
       23. A positive air pressure respirator apparatus comprising a face piece or mask covering at least the mouth or nose of a wearer, a pump unit arranged to supply air to the space within the face piece or mask, an electric motor within the pump unit arranged to drive a fan, wherein the apparatus is provided with actuable control means adapted to cause the apparatus to undergo a calibration phase such that the speed of rotation of the fan is set at a pre-determined optimum base value relative to the operating conditions then prevailing in the apparatus. 
     
     
       24. A positive air pressure respirator apparatus comprising a plurality of parts including a face piece or mask covering at least the mouth or nose of a wearer, a pump unit arranged to supply air to the space within the face piece or mask, an electric motor within the pump unit arranged to drive a fan, at least one filter to filter air entering the face piece or mask, a valve controlling the flow of air from the pump unit to the face piece or mask during inhalation and from the face piece or mask during exhalation, the valve including an air outlet valve which is maintained in a closed position during inhalation by air pressure from the pump unit, and a performance monitoring means for some or all of the parts which provides at least one signal that informs the wearer of the condition of some or all of the parts, wherein the signal is generated externally to the face piece or mask and is fed to the face piece or mask for detection by a wearer. 
     
     
       25. A forced air breathing apparatus comprising a face piece or mask for covering at least the nose or mouth of a wearer, a pump unit arranged to supply air to a space within the face piece or mask, an electric motor within the pump unit arranged to drive a centrifugal fan, means for monitoring and controlling the speed of the motor so that the fan rotates at a substantially constant speed during its operation, a filter to filter air entering the face piece or mask and a valve controlling exhalation of air from the face piece or mask by a user. 
     
     
       26. A forced air breathing apparatus comprising a face piece or mask for covering at least the nose or mouth of a wearer, a pump unit arranged to supply air to a space within the face piece or masks, an electric motor within the pump unit arranged to drive a fan forming part of the pump unit, and a first valve controlling exhalation of air from the face piece or mask by a user, the apparatus including a second valve controlling the flow of air through the pump unit, the second valve being arranged to close when the pressure present within the breathing apparatus downstream of the fan rises to a predetermined level.